The present invention relates to an optical disk capable of recording and reproducing, such as a magneto-optical disk and a phase-change optical disk, in particular, to an optical disk with an easy formatting procedure.
Optical disks are explained in page 151 to page 196 of "Video Disk and Digital Audio Disk for Beginner's: compiled by Soichi Iwamura" published by Corona Co., Ltd. The production process of an optical disk will be explained simply. An original plate is prepared by applying a glass plate with a photo resist. The original plate is irradiated with a laser light beam by an exposing device so as to expose the photo resist. Then a pit or a groove is formed on the original plate by eliminating the exposed portion by the developing treatment of the photo resist. A disk plate is produced by the injection molding, utilizing a stamper formed by the original plate. An optical disk capable of recording and reproducing can be formed by forming a recording film on the disk plate. In the case of an optical disk dedicated for reproduction, an optical disk is produced by forming a reflecting film on a disk plate formed by the use of a stamper with the information pit already formed on an original plate.
Among these optical disks, in particular, a magneto-optical disk and a phase-change disk are used as the optical disks capable of recording and reproducing.
The magneto-optical disk is produced by forming a recording film comprising a ferromagnetic perpendicular magnetization film on a substrate. Information is recorded by generating a magnetic domain corresponding to the recording information in the recording film by condensing a light beam onto the recording film as well as applying a magnetic field. The recorded information can be reproduced by utilizing the change of the Kerr rotation angle, which depends on the orientation of the magnetic domain of the recording film.
On the other hand, information is recorded in the phase-change disk by selectively forming a crystalline portion and an amorphous portion in a recording film by utilizing the heat generated by condensing a light beam on the recording film. The recorded information is reproduced by utilizing the difference in the amount of the reflected light between the crystalline portion and the amorphous portion.
In either the magneto-optical medium or the phase-change medium, a light beam follows a track so as to utilize a land or a groove on the recording medium for controlling the tracking during recording or reproduction.
In soft-formating type optical disk as an optical disk capable of recording and reproducing, since ID information by a pre-pit such as address information is not recorded immediately after the production, the optical disk needs to be formatted by recording the ID information before use in order to record information. In this case, in conventional optical disks such as a magneto-optical medium and a phase-change medium, only a groove is formed on a face of the disk so that a starting point of formatting is not particularly defined.
Therefore, in formatting an optical disk by an optical disk drive device, the starting point of formatting is determined by the mechanical position of the drive device. This may result in the irregularity of the radius position with respect to the address information or incomplete formatting due to misplacement of the formatting starting point caused by disturbance so that a predetermined domain of the disk cannot be formatted.